This change adapts doc examples to Python 3 so they work on current
installations.

python.texi uses a mixture of Python 3 and Python 2 print syntax, the
latter having been sunsetted several years ago.

Adding Eli as "Responsible Maintainer" for documentation.
Also adding Simon Marchi who from recent commits may have an interest in this
part of GDB and may have comments or suggestions.

Perhaps this patch falls under "The Obvious Fix Rule".
The patch is provided inline for critique and also as attachment.
If I have missed any conventions please state so.